The Intel K processors are the unlocked ones, yes. If you don't increase voltage, overclocking is generally safe.
A cheap no-name PSU may be unfit for purpose. Likely good for no more than 60% of its label, it may also be missing protection circuits, such that it could die at any time for indeterminate causes (e.g. a power fluctuation), and/or damage attached parts. The long term health and stability of a system is dependent on the quality of its PSU, so that's not the place to go cheap. I'd recommend one of the Seasonic "G" series units, such as the 550W model. Less expensive but still good is the 500W Antec Earthwatts. Of the two, the Seasonic is considerably superior, in features (like modular, sleeved cables) as well as performance (efficiency, stability). Between those, one of the Seasonic-built XFX units would be good too.